The present disclosure relates to image forming apparatuses and particularly relates to an image forming apparatus which can calculate the remaining amount of paper sheets through a single analog input port and can control the movement of a lift plate in a paper feed cassette on the part of the paper feed cassette.
Various types of detection in an image forming apparatus, such as a printer, are increasingly performed by digital processing. For example, the detection of the remaining amount of paper sheets is conventionally performed by four-stage digital processing using at least two sensors. For this purpose, at least two digital input ports are provided in the image forming apparatus.
A digital input port is necessary for each sensor. Therefore, with increasing number of parameters to be processed because of added functions, the required number of ports also increases. In addition, when the number of ports increases, the cost for the CPU of the image forming apparatus accordingly increases. Therefore, there is a challenge in that high functionality needs to be achieved while the required number of ports is reduced as much as possible.
An image output device is known which, to address the above challenge, includes a paper cassette capable of storing recording paper sheets, a movable part movable according to the remaining amount of recording paper sheets in the paper cassette, and a remaining paper amount detecting section configured to detect the remaining amount of paper sheets in the paper cassette by detecting the position of the movable part. In this case, the detection of the remaining amount can be displayed in multiple steps using a single analog input port. Thus, an image output device can be provided which can detect the remaining amount of paper sheets with a simple structure or can continuously detect the remaining amount of paper sheets with a simple structure.
Alternatively, an image forming apparatus is known in which units internally equipped with a short circuit can be installed into the apparatus body. The image forming apparatus includes: a first body-side connecting part operable to, upon installation of one or more units into the apparatus body, connect one or more separate resistive elements provided inside the apparatus body, one separate resistive element for each unit, to their respective associated short circuits and apply voltage to the separate resistive elements; and a second body-side connecting part operable to, upon selective installation of at least two units into the apparatus body, connect a common resistive element, which is provided inside the apparatus body and can be shared among the at least two units, to the short circuit of the installed one of the at least two units and apply voltage to the common resistive element. The image forming apparatus further includes an installation status determining section configured to, based on the voltage applied to the separate resistive elements and/or the common resistive element owing to the installation of the unit or units, the status of installation of the unit or units installed in the apparatus body with some exceptions. Thus, as for the units selectively installed, there is no need to provide their individual resistive elements. As a result, the number of resistive elements used can be reduced, resulting in cost reduction of the image forming apparatus. Furthermore, the voltage applied to the separate resistive elements and/or the common resistive element is detected through a single detection port. Therefore, the number of signal lines and detection ports for use in detecting whether or not each of optional units, a developing unit, a photoconductor unit, and so on is installed can be reduced, resulting in line saving and cost reduction.